The double-chambered grand option, comprising measurements to assist with 5 Blow distance 43mm-47mm, 5 Set off/let off 2mm-6mm, 5 Damper lift, 21.5mm-23mm can also be used to help judge checking, 5 Key height 62mm-66mm. More stable than wood in order to stay accurate but still flexible. Made in an ivory colour to enable easy reading when in action. Individually marked for ease of use and supplied in a purpose-made compact and protective case. The guides are designed in a stable thermoplastic polymer made strictly from renewable resources generated from biodegradable materials like cornstarch, which is softer than copper so as not to damage bass strings when in contact but a climatically stable material unlike wood, staying accurate but still flexible